Anterior uveitis

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Anterior uveitis in a cat caused by FIP
A 6-year-old Domestic shorthair cat. The darker iris in the right eye is associated with a previous iritis
An 8-month-old Domestic shorthair cat with bilateral anterior uveitis associated with FIP. In the left eye hemorrhage (hyphaema) and fibrin obscure the underlying changes int he iris which are more severe and have been present for longer than those in the right eye. The kitten also had neurological deficits

Anterior uveitis is an inflammatory disease of the uvea (anterior chamber of the eye), and may primarily involve the iris (iritis) or both the iris and the anterior part of the ciliary body (iridocyclitis). This disease is commonly seen in cats with FHV and FIP infection as well as trauma.

Intermediate uveitis predominantly involves the posterior part of the ciliary body (pars planitis). Posterior uveitis primarily involves the choroid (choroiditis), but close association of the retina means that inflammation of both choroid and retina is the usual situation. Panuveitis is inflammation of the entire uveal tract - iris, ciliary body and choroid[1].

Uveitis in cats may occur spontaneously or secondary to systemic disease. Spontaneous uveitis is often granulomatous, characterized by nodular lesions within the iris stroma and altered iris coloration. Flare and corneal oedema are often absent but multifocal deposits (keratic precipitates) may occur on the corneal endothelial surface. The condition may be unilateral or bilateral and is usually responsive to steroids (systemic and subconjunctival). Long-term therapy is often required and secondary glaucoma is a major concern[2].

Causes

  • Exogenous causes such as trauma and corneal ulcers
  • Endogenous causes such as :
Neoplasia - lymphoma
Allergy/immune-mediated - Eosinophilic keratitis
Viral - Feline herpes virus, Feline leukemia virus, Feline immunodeficiency virus, Feline infectious peritonitis virus, Feline calicivirus
Parasitic - Coccidia (Toxoplasma spp), Fungi (Cryptococcus spp, Histoplasma spp, Blastomyces spp, Coccidioides spp, Candida spp) - very rare
Lens luxation
Idiopathic (lymphocytic-plasmacytic anterior uveitis)

Clinical signs

Clinical signs of anterior uveitis are not usually diagnostic of the cause of endogenous uveitis, whereas the exogenous causes (e.g. trauma) are often apparent.

Acute uveitis is unusual in cats except for that associated with trauma. There is rarely intense pain seen in dogs and horses and many cats are first presented when the ocular manifestations have become subacute.

Clinical signs include pain, photophobia, blepharospasm, lacrimation, hyperemia of visible vessels, aqueous flare, hyphaema, miosis, low intraocular pressure and a swollen iris with loss of iris detail. There may also be posterior segment involvement, including optic neuritis and intraocular hemorrhage. Vision can also be affected.

Chronic uveitis is the commonest presentation of feline uveal tract inflammation and the extensive range of appearances are rarely diagnostic for any specific cause. Owners often cite alteration of appearance, especially a change of iris colour as a reason for seeking professional advice.

Treatment

Successful management of anterior uveitis relies on adequate diagnosis of underlying cause. In addition to treating the underlying cause, specific treatments for anterior uveitis usually consist of anti-inflammatory agents and mydriatic cycloplegics (drugs which dilate the pupil).

  • Corticosteroids

Corticosteroids topically and/or systemically are the commonest type of anti-inflammatory agent used in the treatment of this disease. Prednisolone acetate 1%, dexamethasone 0.1% and betamethasone sodium phosphate 0.1% are potent topical preparations; prednisolone acetate being the most effective.

Corticosteroids should not be used if there is corneal ulceration present. Systemic corticosteroids should be avoided if there is a suspicion of systemic disease causing the anterior uveitis (e.g. FHV, FeLV, FIV). Reactivation of latent herpes virus disease is a potential complication of corticosteroid usage.

  • NSAIDs

Non-steroidal anti-inflammatory agents can be used topically in situations where topical corticosteroids would be contraindicated. However, these agents will modify healing, so patients should be monitored carefully. Topical NSAIDs are more commonly used as an adjunct to ocular surgery

  • Mydriatic cycloplegics

Atropine 1% ointment is the drug of choice for effecting mydriasis (dilation of the pupil). Phenylephrine 10% is not particularly effective in cats (possibly because the dilator muscle of the cat's iris has both an adrenergic and cholinergic nerve supply) and is not used therapeutically (Barnett & Crispin, 2002).

The patient's progress should be monitored closely and the aim is to eliminate pain (by relaxing ciliary spasm) and to reduce the risk of synechiae formation. This can be achieved with moderate pupillary dilation and mydriatic cycloplegics should then be applied only as often as in necessary to maintain this state of mydriasis.

  • Antivirals

Famvir is indicated at 50-250mg/kg once daily if FHV is suspected as a triggering cause of uveitis

Oral melatonin at 0.5 - 1.0 mg daily has been used experimentally as a therapy in acute uveitis in cats[3].

Complications

Some types of uveitis respond poorly to treatment, especially if there is a systemic disease involved.

Glaucoma is an uncommon sequel to uveitis in the cat compared with the dog, but when it does occur, particularly in those cats which are seropositive for Toxoplasma goondii, it can be very difficult to treat, especially if additional problems arise in the form of corneal decompensation with epithelial erosion, visual loss, or globe enlargement.

For acute uveitis and secondary glaucoma more intensive use of anti-inflammatories, possibly combined with a short-acting mydriatic (tropicamide 1%) and carbonic anhydrase inhibitor may be required, but such cases often respond poorly. When active uveitis is accompanied by both secondary glaucoma and corneal erosion, effective management becomes impossible and, if the underlying uveitis cannot be controlled, it is better to remove the affected eye. Cats manage eye loss of vision extraordinarily well and their quality of life will be affected more by the presence of a blind painful eye than by its absence.

Lens luxation is not an uncommon complication of chronic uveitis, but in cats, unlike dogs, it is not an emergency and secondary glaucoma is less likely as a consequence of initial luxation.

References

  1. Crispin, Sm (1993) The uveal tract. In Petersen-Jones, SM, Crispin, SM (eds) Manual of Small Animal Ophthalmology, pp.173-190. BSAVA Publications, Cheltenham
  2. Barnett, KC & Crispin, SM (2002) Feline ophthalmology: An atlas and text. Saunders, USA
  3. Del Sole MJ et al (2011) Therapeutic benefit of melatonin in experimental feline uveitis. J Pineal Res Jun 9
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